In order to produce batteries having a markedly higher energy density, currently, the lithium-sulfur battery technology is being researched, via which the energy content of currently 200 Wh/kg can theoretically be increased to above 1000 Wh/kg.
In order to achieve an energy content of above 1000 Wh/kg, however, the cathode would have to be formed completely of elemental sulfur. However, elemental sulfur is neither ionic nor electrically conducting, and so additives must be added to the cathode which markedly reduce the theoretical value.
A further problem is the solubility of the polysulfides Sx2- that are formed during discharge (reduction). These can migrate to the lithium anode and be reduced there, in such a manner that no electric current can be produced therefrom. This process is generally termed shuttle mechanism, and leads to a further decrease in the energy density.